The purpose of the proposed research is fivefold: 1) To define, on the electron microscopic level, cytoplasmic changes during early degenerative and reactive stages in neurons following mechanical trauma. 2) To characterize the sequence of events in the destruction and removal of the myelin sheath following sectioning of partially myelinated axons in living tissue cultures. 3) To elucidate patterns of connectivity between neurons in living cultures by marking single neurons with dye or radioactive tracers. 4) To continue work on the biology and histotypic development of the retina in vitro. 5) To characterize membrane properties of cell surfaces necessary for the initiation of myelin formation in tissue cultures.